In a so-called crystalline photoelectric conversion device, a cover glass is generally arranged on the light incident side. However, when the photoelectric conversion device is installed on the roof of a house, light reflected from the cover glass may cause annoyance to the neighborhood in some cases. Therefore, a cover glass having an uneven surface so as to disperse the reflected light is used in applications that require attention to the reflected light, such as those used on the roof of a house.
Since the shape of the surface roughness affects the quantity of light to be transmitted through the cover glass, there have been reported attempts to optimize the shape of the surface roughness of the cover glass for improving the photoelectric conversion efficiency. For example, JP 2003-243689 A (Patent Literature 1) discloses a cover glass having a surface formed with hemispherical recesses. In this cover glass, the shape and arrangement of the recesses are designed so as to increase the quantity of light to be transmitted through the cover glass during the day throughout the year. In the case of forming recesses for such a purpose, the depth of the recesses is set to be greater than in the case for the purpose of imparting only an antiglare function.
Meanwhile, in some cases, a reflection-reducing film may be formed on the surface of a transparent base in order to increase the light transmittance of the base represented by a glass sheet. Although the most commonly used reflection-reducing film is a dielectric film obtained, for example, by vacuum vapor deposition, sputtering, or chemical vapor deposition (CVD), a fine particle-containing film that contains fine particles such as silica fine particles also may be used in some cases as the reflection-reducing film. The fine particle-containing film can be formed by applying a coating solution containing fine particles onto a transparent base by a method such as dipping, flow coating, or spray coating.
JP 2007-121786 A (Patent Literature 2) discloses the formation of a fine particle-containing film as a reflection-reducing film, though it is formed not on the cover glass but on the surface of a glass substrate of a photoelectric conversion device of the so-called thin film type. However, for the glass substrate used in such a photoelectric conversion device of the thin film type, a float glass having smooth surfaces is employed, as has been disclosed in this publication.